Datasheet

_
+
IN-
IN+
PWM H-
Bridge
V
O+
V
O-
Internal
Oscillator
C
S
To Battery
V
DD
GND
Bias
Circuitry
R
I2
R
P
Filter-Free Class D
SHUTDOWN
R
I1
Single-Ended
Input 2
C
I2
C
P
Single-Ended
Input 1
C
I1
1 nF
Ferrite
Chip Bead
V
O−
V
O
+
Ferrite
Chip Bead
1 nF
TPA2011D1
SLOS626A –DECEMBER 2009–REVISED MAY 2010 www.ti.com
Figure 33. Application Schematic With TPA2011D1 Summing Two Single-Ended Inputs
WHEN TO USE AN OUTPUT FILTER
Design the TPA2011D1 without an Inductor / Capacitor (LC) output filter if the traces from the amplifier to the
speaker are short. Wireless handsets and PDAs are great applications for this class-D amplifier to be used
without an output filter.
The TPA2011D1 does not require an LC output filter for short speaker connections (approximately 100 mm long
or less). A ferrite bead can often be used in the design if failing radiated emissions testing without an LC filter;
and, the frequency-sensitive circuit is greater than 1 MHz. If choosing a ferrite bead, choose one with high
impedance at high frequencies, but very low impedance at low frequencies. The selection must also take into
account the currents flowing through the ferrite bead. Ferrites can begin to loose effectiveness at much lower
than rated current values. See the TPA2011D1 EVM User's Guide for components used successfully by TI.
Figure 34 shows a typical ferrite-bead output filter.
Figure 34. Typical Ferrite Chip Bead Filter
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